Note: Descriptions are shown in the official language in which they were submitted.
~048902
This invention relates to a device for e~erting back-
pull on the heddles of Jacquard looms. In the production of
woven patterns, Jacquard looms lift or lower certain warp
threads so that either a top shed or a bottom shed is formed
through which the weft thread is shot. In order to enable
the warp thread to be pulled upwardly or downwardly from its
median position so as to form the shed, the warp thread runs
through a thread ring on a vertically disposed heddle. The
upper end of the heddle is connected to a patterning machine,
whereas its lower end is engaged by a pulling device which
applies the necessary pull on the heddle in the direction
opposite to that applied by the patterning machine.
In its simplest form, the pulling device may be a
weight suspended from the heddle. The speed of the return
movement of the headle depends, in this case, upon the speed
at which the weight drops. Since modern looms operate at
rather high speeds, the speed at which the weight drops is no
longer sufficient for pulling back the warp thread at the
required speed. In order to increase the pu~l-back speed,
~o weights have been replaced by helical spri.ngs which exert a
resilient return force on the warp threads. ~owever, helical
springs of the necessary type have relatively large radial
dimensions, and this has been found to be very disadvantageous
in instances where a large number (several thousands) of
heddles are arranged side-by-side.
; It is also known to utilize rubberized springs as
return elements to en~age the heddles. Such springs are dis-
closed in German patent specification OS 1 962 826. Although
these springs are of small three-dimensional size, they result
in considerable lost work, since the return force, as in the
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~(~489~Z
case of helical sprinc3s, varies in dependence upon the distance
traveled. Extension of the spring element is at its minimum
in the b~ottom shed. In this position, the spring must apply
certain tensile force to insure that a neat shea is formed.
However, the return force does not need to be greater in any
other shed position (middle or top shed). Nevertheless,
because of the resilient properties of a spring, the return
force becomes greater in the other shed positions. The effort
required to overcome the increasing tensile forces during
o lifting of the shed represents nothing more or less than lost
work. This lost work increases with the steepness of the
spring characteristic curve. In practice it has been found
that springs with particularly flat characteristic curves, i.e.
springs involving little lost work, do not retain their initial
length during long-term operation. In order to obtain the
necessary tensile force in the bottom shed position, these
springs have to be continuously adjusted. HQwever, the adjust-
ment can only be utilized if the space conditions in the loom
permit, or until breakage due to excess stretching takes place.
~o This is discussed in the article of Dr. Ing. Adolf Funder,
Ing. (grad.) Hugo Griese; MELLIAND TEXTILBERICHTE 2/1974, p.105
et seq.
The primary object of this invention is to provide a
back-pull device for heddles of a Jacquard loom that exerts a
substantially constant return force irrespective of the shed
position and at the same time permits a very rapid mode of
operation.
In accordance with this invention, the object is
achieved by way of a piston which is displaced in a substan-
tially air-tic3ht manner in a cylinder guide. The piston is
fitted in the lower end of a respective heddle and the
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104890Z
cylinder guide is carried by a wall of a chamber in which a
pressure, different from atmospheric pressure, is maintained.
In accordance with the invention, each heddle is
connected to its associated piston. The piston moves in the
guide cylinder. ~11 the guide cylinders extend into a common
vacuum or high-pressure system so that the same pressure and,
therefore, the same force is applied to all pistons. The guide
cylinders do not necessarily have to be of circularcross section
but may be of some other cross section, such as oval, to
prevent rotation of the pistons which pistons are, of course,
of the same cross section as the respective cylinders.
The chamber should be of such size that the pressure
within the chamber does not alter substantially even when all
the pistons are displaced in the same direction at the same
time so that the same return force is continuously exerted on
each piston irrespective of its position. No increase in
force has to be overcome when lifting the shed, so that no loss
of work occurs. The magnitude of the tensile force is deter-
mined by the si?.e of the piston face and the differential
~o between the pressure within the chamber and atmospheric
pressure. The tensile force can thus be adapted to suit all
practica] requirements.
In the further advantageous form of the invention, the
cylinder guides are open at the top and, at their lower ends,
lead into the chamber in which a vacuum is maintained. A
vacuum chamber of this kind can be achieved simply by connect-
ing a suction pump to the chamber. Atmospheric pressure acts
on one end of each of the pistons and the vacuu~ within the
chamber acts on the opposite end~
In an alternative arrangement, the cylinder guides are
3o
~ open at their bottom ends and their upper ends lead into the
1(1 4~90Z
chamber in which a pressure greater than atmospheric pressure
is maintained. This system presupposes either a complicated
arrangement for guiding the heddles or the passage of the
heddles through the high pressure chamber. This pressure
system does not necessarily have to be operated pneumatically.
Instead it may be operated hydraulically and the hydraulic
medium attends to force the pistons out of the chamber against
the pulling action of the heddles. Any fluid that may lea~
out between the pistons and the cylinders can be trapped in a
~0 sump and pumped back into the chamber.
The cylinder guides are preferably arranged in the wall
of the chamber with the same spacing as that of the holes in
a harness board which determines the spacial distribution of
the heddles. The bores in the cylinders can be arranged very
closely side-by-side in the chamber wal]. so that the heddles
extend precisely vertically from the chamber to the harness
board. The chamber wall, like the pistons which slide, one in
each of the cylinder guides, can be formed of a plastics
material. If required, that zone in which the cylinder guides
are a-rranged rnay also be larger than the perforated zone of
the harness board. In such event, it is either necessary to
deflect the heddles or to arrange a large nurnber of cylinder
guides in inclined positions.
Although a pneumatically operated device for lifting
and lowering the warp thread in loorns is!known from German
patent specification OS 2 248 656, in such device each thread
ring is individually pneumatically controlled. The thread
rings are secured to rigid piston rods which can move upwardly
for forming the top shed, as well as downwardly for forming
~o the bottom shed. In that apparatus, the known Jacquard machine
1048902
is replaced by a pneumatic control means and the piston rods
are likewise returned by means of helical springs.
With the above, and other objects in view that will
hereinafter appear, the nature of the invention will be more
clearly understood by reference to the following detailed
description, the appended claims and the several view illus-
trated in the accompanying drawings.
IN T~IE DRAWINGS:
Figure 1 is a diagrammatic view illustrating the forma-
o tion of the bottom shed and the top shed in the Jacquardmachine and illustrating a return spring as the ~ack-pull means.
Figure 2 is a schematic end view of a loom showing the
arrangement of the heddles, the patterning machine, the harness
cords and the harness board with a vacuum being utilized for
exerting the return forces.
Figure 3 is a schematic end view similar to Figure 2
and shows the use of a super atmospheric pressure for exerting
the return forces.
Figure 4 is an elevational view with parts broken away
of a heddle having a piston fixedly secured thereto, the piston
being shown in section.
Figure 5 is a plan view with parts omitted showing a
modified arrangement of chambers and cylinder guides.
Figure 6 is a fragmentary vertical sectional view taken
along the line 6-6 of Figure 5 and shows the specific canstruc-
tion of one of the cylinder guides in its associated chamber.
Figure 7 is a schematic side elevational view showing
the arrangement of distributing ducts and cylinders leading
therefrom wherein the heddles are very closely spaced and
wherein the ducts and cylinders are arranged in several differ-
ent levels and in laterally offset relation.
iO~89QZ
Fig~lre 8 is an schematic longitudinal section of an
alternative embodiment of the invention.
Referring now to the drawings in detail, reference is
first made to Figure 1 wherein there is illustrated the move-
ment of a warp thread 10 during the formation of the bottom
shed 11 and the top shed 12. The warp thread is passed through
a thread ring 1~ which is formed in a metal wire and the
position of which above the associated heddle 14 is controlled -
by the conventional patterning machine. In previous machines,
~o a return weight was fitted at the lower end of the heddle
whereas in more modern machines the return force is applied by
a tension spring 15 which takes the form of either a helical
spring, as illustrated, or a rubberized spring. It is to be
understood that the arrangement shown in Figure 1, particularly
the return spring 15, is conventional.
Referring now to Figure 2 it will be seen that there
is illustrated a machine frame 18 of a loom, other features
of the loom being omitted for purposes of clarity. The machine-
frame 18 includes upper transverse beams 19 to which a pattern-
ing machine 20 is secured. Extending from the patterning
machine 20 are harness cords 21 which are arranged in diverging
relation and which individually control the level of thread
rings 13 of each of the numerous warp threads. As a rule,
several thousand harness cords 21 are present to control the
level of a like number of warp threads.
The spacial distribution of the harness cords 21 emerg-
ing from the patterning machine 20 is effected by a harness
board 16 which is carried by the frame 18 below the patterning
machine 20. It is to be understood that the harness board has
~o a plurality of rows of holes through each of which passes an
individual harness cord 21. Although only three harness cords
have been shown in the drawing, it is to be understood that a
iO48902
large number of ~urther harness cords are present hetween
those specifically illustrated. A fanned out distribution of
the harness cords in the harness board 16 is necessary because
it is impossible to arrange the harness cords side-by-side
in a row in the same close proximity as that of the associated
warp threads 10 when the latter are brought into the weave. --
The patterning machine 20 pulls on the individualharness cords 21 and in this manner the individual thread rings
13 are actuated in a particular patterning program. The harness
cords 21 are pulled back by a back-pull device 22 which is the
subject of this invention. The device comprises a plate 17
which forms the wall of a chamber 24. The upper surface of
the plate 17 has extending therefrom numerous cylinder guides
23 which project downwardly into the interior of the cham~er.
The cylinder guides are open at both ends with their lower
ends opening into the chamber 24. A vacuum is maintained
within the chamber 24 by means of a suction pump 25.
~ piston 26 is mounted in each cylinder guide 23 for
displacement relative thereto. It is to be understood that
~o the relationship of each piston 26 with respect to its cylinder
guide 23 is such that a substantially air-tight seal is obtained.
Each piston 26 is connected to the lower end of a heddle 14 and
is drawn into the chamber 24 by the vacuum produced in the
chamber.
It is to be understood that the suction force applied
on each piston 26 remains constant irrespective of the position
of that piston in its cylinder guide. If the area of the
piston face is, for example, 12 mm (corresponding to a diameter
of approximately 4 ~m), the return force exerted on the piston
grams
~o is approximately thirty ~e~s at 0.75 bar. The length of each
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1[)4~9~Z
cylinder guide is selected to correspond with the depth of
the shed which is to be effected so that the pistons 26 do
not move completely out of their cylinder guides during the
operation of the loom.
The cylinder guides have a spacing equal to that of
the holes in the harness board 16 so that the heddles 14 move ~
rectilineax and vertical between the harness board 16 and the
plate 17 and cannot be deflected~
Reference is now made to Figure 3 wherein in lieu of
o a vacuum chamber 25, a positive pressure chamber 28 is pro-
vided. The chamber 28 has the plate 17 forming the bottom
wall thereof with the cylinder guides 23 again projecting into
the interior of the chamber, but upwardly instead of downwardly
as shown in Figure 2. Pressure is maintained in the chamber 28
by means of a compressor type pump 29.
It is to be noted that the heddles 14 extend from the
pistons 26 through the pressure chamber 28 from which they
emerge through an upper wall 30 of the chamber. In order to
maintain a seal of the chamber 28, suitable sealing elements
~o 31 are carried by the wall 30 and sealingly engage respective
ones of the heddles. It is to be understood that the pressure
in the chamber 28 drives the pistons 26 downwardly and thus
~ heddles
applies a constant tensile force on the hcadcr3 14.
Reference is now made to Figure 4 wherein a typical
heddle construction is illustrated. It is to be noted that
- each heddle 14 is provided intermediate its ends with a thread
ring, the lower end of the heddle is secured in a fixed manner
to the associated piston 26. The heddle 14 is formed of a wire
to the lower end of which is attached the piston 26 which is
preferably formed of plastics material. The piston 26 is
integrally connected with the wire by injection molding and,
1~)4890Z
therefore, cannot be detached from the wire without being
destroyed. At the upper end of the heddle 14 is a further
ring 30 through which a harness cord 21 is secured to the
heddle.
The device of this invention offers the advantage that
only the absolutely necessary tensile force is applied over
the entire displacement distance of the individual heddle.
Since no lost work must occur, the patterning machines,which
have to operate in a direction opposite that of the back-
~o pulling devices, can be of correspondingly lighter construction,i.e. they can exert lower tensile forces than in a case where
the known pulling devices, such as springs or weights, are
used. Further, it will be readily apparent that the pattern-
ing machine is subjected to treatment that causes less damage.
A further advantage of the invention resides in the
fact that the tensile force applied to each heddle is infin-
itely variable since the pressure differential on a piston 26
can be suitably varied by altering the pump capacity and thus
varying the pressure wib~lin the associated chamber. None of
~o the known back-pulling devices permit the use of such infin-
itely variable tensile force.
~ t this time it is pointed out that if more than one
loom are present, their pulling devices can be connected to a
common pressure or vacuum source. In this case, only a single
pump and/or a single pressure chamber is ~required. The pressure
chambers into which the cylinder guides directly lead can,
therefore, be smaller, and this represents an advantage as
regards assembly of the equipment.
Reference is now made to Figures 5 and 6 wherein in
30 lieu of the cylinder guides 23 beil!g carried by a single large
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chamber, plural ducts 35 are provided and each duct carries
at least one row of the cylinder guides 23. The ducts 35 are
arranged parallel to each other and the cylinder guides
carried thereby form a set of such cylinder guides. It is to
be understood that the greater the number of ducts 35 or
cylinder guides 23, the closer the thread spacing obtainable
in the woven material. The position of each cylinder guide 23
corresponds to the position of a hole in the harness board 16.
All of the ducts 35 are mechanically connected to a common
transverse bar 36. It is to be understood that the connection
of the ducts 35 to a vacuum source may be accomplished in a
conventional manner by way of hoses. It is also to be under-
stood that the ducts 35 may be supported at both ends thereof
by like bars 36.
- It is to be understood that by utilizing the individual
ducts 35, a very wide variety of thread spacings can be achieved
without having to use a completely new set of cylinder guides
carried by a single plate, such as the plate 17. If the spacing
is to be closer than would be possible with the ducts 35 in
touching engagement, then the ducts 35 may be vertically offset
as is shown in Figure 7, for example. In Figure 7, the ducts 35
are sufficiently vertically offset so that the spacing between
adjacent ducts, at least in the upper layer of ducts, only has
to be slightly greater than the dimension of a heddle 14. It
will be seen that by positioning the lower ducts in alignment
with gaps between the upper ducts, a very close arrangement of
heddles 14 can be obtained.
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UZ
Ref rring now to Figure 8, there lS illustrated a
longitudinal sectlon of another embodiment of the inventlon.
The section of Figure 8 is taken rectangularly wlth respect
to the end views of Figures 2 and 3, but in connection with a
modified example. In Figure 8, the spacing of the cylinder
guides 23 is greater than the spacing of the perforatlons in
the harness board 16 so that each hole in the harness board
is misaligned to the corresponding cylinder guide. To guide
the heddles so that they run at least generally vertlcally wlth
respect to the plate 17 into the cylinder guides 23 a deflection
plate 32 is mounted intermediate the harness board 16 and the
plate 17. The deflection plate has perforations 33 which are
adapted to the spacing of the cylinder guides so that the
- heddles diverge from the harness board to the deflection board,
and underneath the deflection board continue substantially
in parallel into the respective cylinder guides.
~ lthough only several preferred embodiments of back-
pull devices have been specifically illustrated and described
herein, it is to be understood that minor variations may be
made in the back-pull devices without departing from the
spirit and the scope of the invention, as defined by the
appended claims.
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